<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>基础选择器</title>
    <style>
        /*通用选择器*/
        *{
            padding: 0;
            margin: 0;
        }
        /*标签选择器*/
        div{
            width: 200px;
            height: 200px;
            margin: 50px auto;
            border: 1px solid #000;
            background-color: gold;
        }
        h1{
            text-align: center;
        }
        /*类选择器*/
        .box{
            width: 200px;
            height: 200px;
            margin: 50px auto;
            border: 1px solid #000;
            background-color: gold;            
        }
        /*id选择器*/
        #box{
            width: 200px;
            height: 200px;
            margin: 50px auto;
            border: 1px solid #000;
            background-color: gold;                        
        }
    </style>
</head>
<body>
    <h1>三种基础选择器</h1>
    <div>标签选择器</div>
    <div class="box">类选择器</div>
    <div id="box">id选择器</div>
</body>
</html>